1. Field of the Invention
This invention relates to novel phenolic compounds, and a recording material comprising any of the same as a color developing agent.
2. Discussion of Background
Hitherto, various recording materials utilizing a color-developing reaction between colorless or light-colored leuco dyes and color-developing agents, which is initiated with the application of heat or pressure, have been proposed.
Developing and fixing processes are not necessary when images are transferred through a thermosensitive recording material which is one of the above recording materials. Therefore, the thermosensitive recording material does not require a complicated apparatus, and images can be transferred to a recording sheet speedily without generating noise. Furthermore, the price of the thermosensitive recording material is relatively inexpensive.
Because of the above advantages, the thermosensitive recording material is employable in various fields, for instance, for use with terminal printers for computers, facsimile apparatus, automatic ticket vending apparatus, label printing machines, and recorders for various apparatus and instruments.
In general, the thermosensitive recording material comprises as a color-producing dye a colorless or lightcolored leuco dye having an atomic group of lactone, lactam or spiropyran, and as a color developing agent such as an organic acidic material or phenolic material. When the above recording material is employed, images can be obtained with high density without coloring the background of the recording sheet, so that it enjoys general popurality.
With the recent increase of the demand for a recording method using the thermosensitive recording material, the requirement for recording at higher speed is getting greater. In order to meet such a requirement, not only a recorder operable at high speed but also a recording material usable with a high-speed recorder is now being developed.
In order to attain high-speed recording, various manners for improving the sensitivity of the thermosensitive recording material have been proposed.
For instance, some high-sensitive color-developing agents for use in the recording material, such as p-hydroxyl benzoic ester as disclosed in Japanese Laid-Open Patent Application 56-144193, hydroxyl naphthoic ester as disclosed in Japanese Laid-Open Patent Application 59-22793, and phenolic compounds having a thioether group as disclosed in Japanese Laid-Open Patent Applications 59-52694 and 59-73993, have been proposed.
The sensitivity of the recording material can also be improved by incorporating various thermofusible materials therein. As such thermofusible materials, naphthol derivatives and benzyl biphenyls have been proposed in Japanese Laid-Open Patent Applications 58-87094 and 60-82382, respectively.
However, the recording material comprising the above color-developing agent or thermofusible material is not yet satisfactory when the color-developing sensitivity, the whiteness of the background, and the preservability of the transferred images are taken into consideration.
Japanese Laid-Open Patent Application 62-181182 discloses a recording material comprising as a colordeveloping agent a hydroxyphenyl thiol derivative capable of being substituted, and as a thermofusible material an aryl compound. However, this recording material is decolored or becomes white when it is brought into contact with water due to the presence of the hydroxyphenyl thiol derivative, and an increased amount of scum is deposited to a thermal head when images are transferred through the recording material due to the presence of the aryl compound. Furthermore, no specific examples of the substituted hydroxyphenyl thiol derivatives are disclosed in this application.